Field of the Invention
The invention is in the field of syringe technology. In particular, the invention is directed to a syringe having an adjustable penetration depth. The adjustable penetration depth syringe is particularly useful in the context of self-administered drugs such as insulin.
Description of the Related Art
Syringe needles preferably require a penetration depth of 6 mm to 8 mm to penetrate a vial closure. Shorter needles will not consistently penetrate the vial septum, or be able to inject air into the vial and withdraw medication. However, injection lengths shorter than 6 mm are preferred by patients and health care professionals for administering an injection. This is particularly true for injections to be delivered in the subcutaneous region, for medications such as insulin. Recent studies have also shown that the possibility of intramuscular (IM) injections increases with needle penetration depth. For administering injections in the subcutaneous region, the optimal needle length tends to be around 4 mm. Current insulin needles on the market are a fixed length, generally 6 mm, in order to properly penetrate the vial septum. These needles do not provide optimal penetration depth for injection into the subcutaneous space while minimizing risk of intramuscular injection.
U.S. Pat. No. 7,651,512 depicts a propelled lancer which optionally has an adjustable tip portion that permits a user to select a desired depth of stylet penetration from a number of depth-penetration choices. However, the lancer is not a syringe, and the design does not expose a specified needle length for an injection; in fact the needle moves within the device.
Thus, an object of the invention is to provide a syringe having an adjustable penetration depth which can be used both to fill the syringe from a vial at one penetration depth, and administer an injection at an optimal injection depth.
Another object of the invention is to provide a syringe having an adjustable penetration depth to accommodate different injection sites and different medications.
Yet another object of the invention is to provide an adjustable penetration depth device which also shields the syringe and places a protective cover over the needle cannula after use to minimize the risk of accidental needle sticks.
Yet another object of the invention combines the above advantages of adjustable penetration depth with an interchangeable needle-hub assembly, so that different gauge needles may be installed on differently sized syringes.
These and other objects of the invention are achieved with an adjustable collar received on the distal end of a syringe movable between fixed positions to adjust the penetration depth of the needle as described below.